1. Field of the Invention
The present invention relates, in general, to the field of analog and digital signal processing, and more particularly to a pulse-width discriminating Analog-to-Digital (A/D) converter capable of use in electrical or optical applications.
2. Background of the Invention
Electrical A/D converters are well known in the art. One conventional A/D converter is the flash converter type which encodes an analog signal, S, as one of 2.sup.M thresholds. This process requires 2.sup.M -1 comparators to determine a digital signal, D, equivalent to signal, S, where M is the number of bits in signal D. If an 8 bit signal D were required 2.sup.8 -1 or 255 comparators would be needed, which would cause a great deal of signal processing time delay in the system.
Another conventional A/D converter is referred to as a successive approximation or pipeline A/D converter system. In this system, signal S is compared to a reference signal, R. Signal S is then adjusted (S-R if S.gtoreq.R, S if S&lt;R) and then compared with signal R/2. The process of comparing and adjusting the reference signal continues, depending on the precision required, until the appropriate digital number is determined. The pipeline system, achieves the successive approximation technique with cascaded stages starting with the most significant bit.
These processes are slow and cause delays in the system. In addition, while these do work electrically, they are not feasible for optical use.